Abstract:

Bacillus thuringiensis (Bt) is a widely distributed Gram-positive bacterium that can produce a series of insecticidal proteins during its vegetative growth and sporulation phases. It is commonly used as a biocontrol agent in agriculture, forestry and public health practice. The Bt crops developed based on genetic engineering technology provide an efficient and environmentally friendly biological control method for agricultural pest management. However, the extensive and prolonged cultivation of Bt crops has led to the gradual development of Bt resistance in pests, which has greatly reduced the insecticidal effect of Bt proteins and the long-term benefits of Bt crops. In order to gain a deeper understanding of the relationship between the mechanism of action of Bt proteins and the occurrence of Bt resistance in insects, this paper summarized the structural and functional characteristics of various Bt toxins, and elaborated the molecular mechanism of Bt resistance in insects from three main aspects: immune system regulation, changes in toxin activation, and mutations in toxin receptor genes. In addition, two insect resistance management strategies, gene stacking and ‘high dose/shelter’ were also introduced. Finally, the future research directions of Bt crops were pointed out, including further in-depth analysis of the mode of action of Bt toxins and the mechanism of Bt resistance in insects, exploration of new Bt proteins, strengthening the popularization and publicity of Bt crops, and establishing resistance monitoring network as well as early warning system.

Key words: Bacillus thuringiensis, Cry protein, insecticidal activity, toxin receptors, resistance mechanism, resistance management, insecticidal proteins, genetic engineering, biological control